Queensland Nut Tree Macadamia Intergrifloia
Total Page:16
File Type:pdf, Size:1020Kb
Queensland nut tree Macadamia integrifolia There are seven Macadamia species native to Australia, with the Queensland nut tree Macadamia integrifolia being one of two species that have an edible nut. The attractive foliage and flowers M. integrifolia have made it a popular tree for domestic yards. It is also the species most commonly used for commercial production of nuts, although it is often crossed with other Macadamia species. Wild populations of M. integrifolia are rare and have a restricted and scattered distribution in Photo: CSIRO Plant Industry rainforest throughout south-east Queensland from Bauple (about Description 30km south of Maryborough) in Macadamia integrifolia is a rainforest species endemic to Queensland. It is also known as the smooth-shelled macadamia, bush nut, nut oak, Queensland nut, Bauple nut or the north, south to Nicoll Scrub bopple nut. Macadamia species, like banksias, waratahs and grevilleas, are members of near the New South Wales the Proteaceae family. border. M. integrifolia is in M. integrifolia can grow to 20m in height with a similar foliage width, giving the tree a danger of becoming extinct in round shape. The trunk is rough but not furrowed, without buttress roots, and reaches a the wild due to extensive diameter of around 30cm. M. integrifolia leaves are thick and leathery, growing to 14cm clearing of its rainforest habitat and arranged on branchlets in groups of three. Mature leaf edges are smooth, but newly formed leaves have a spiny margin. Flowers are cream/white in colour on racemes up to in south-east Queensland for 30cm in length that grow from the leaf axil and hang down from the branches. The green rural and urban development. leathery outer shell (also known as a pericarp or seed vessel) is around 2.5–3.5cm in size and surrounds a smooth brown nut-shell containing a white edible kernel. Flowering has been recorded from August to October, with fruiting from December to March. M. integrifolia is the most popular species used worldwide for commercial production of macadamia nuts. These commercial tree varieties are often smaller than naturally- growing species. Macadamia nut farmers have been selectively grafting M. integrifolia with other Macadamia species (frequently M. tetraphylla) to increase desirable The macadamia nut is the commercial qualities such as a thinner shell, increased yield and disease resistance. only Australian native The National Macadamia Germplasm Conservation Program, an initiative of the produce that has achieved Commonwealth Scientific and Industrial Research Organisation (CSIRO) and the major commercial success. Australian macadamia industry, is establishing plantations of all wild varieties of Macadamia with the aim of having a stock gene pool to aid preservation of the species and provide readily available resources for commercial research. Queensland nut tree Macadamia integrifolia Habitat and distribution M. integrifolia was originally associated with subtropical rainforest that was spread along a 600km coastal strip between Grafton in New South Wales and Maryborough in Queensland, extending up to 150km inland. Current distribution of wild M. integrifolia appears to be similar to the initial distribution area, however populations are more sparsely distributed, and overall numbers have declined as a result of agricultural and urban development. Although M. integrifolia is a rainforest species they tend to grow better in partially open areas such as rainforest edges. They can be found at elevations near sea level up to 600m, preferring well-drained sites on hill crests, hill slopes, scree slopes, foot slopes and along the edges of hoop pine Araucaria cunninghamii scrubs and creek beds. M. integrifolia grows best in mild frost-free weather with reasonably high rainfall and has been recorded fruiting as far south as Sydney. At many sites where M. integrifolia occurs there are less than ten plants remaining. The largest populations are recorded in Amamoor State Forest, Bahr’s Scrub, Nicoll Scrub and Triunia National Parks, and they also occur in several other national parks and state forests as well as three nature refuges. M. integrifolia grows in complex notophyll vine forest, simple notophyll vine forest and in simple microphyll-notophyll vine forest with emergent Araucaria and Argyrodendron species. It can be found in uniformly dark surface soils that vary in texture from clayey sand through various types of loam to silty clay. Leaves, flowers and nuts of Macadamia integrifolia. Photos: CSIRO Plant Industry Naturally occurring Macadamia integrifolia have always been recorded in areas associated Distribution of Macadamia integrifolia in Queensland. Map: EPA with subtropical rainforest. Queensland nut tree Macadamia integrifolia There are nine Macadamia species, seven of which are endemic to Australia, and two species (M. hildebrandii and M. erecta) that are native to the island of Sulawesi in Indonesia. The Australian native species can be divided into two distinct groups — the tropical species found in Far North Queensland (M. claudiensis, M. grandis and M. whelanii) and the subtropical species found in south-east Queensland (M. jansenii, M. integrifolia, M. tetraphylla and M. ternifolia). Distribution of the two edible species, M. integrifolia and M. tetraphylla, extends to northern New South Wales. Macadamia species in south-east Queensland Macadamia tetraphylla Macadamia ternifolia Macadamia jansenii M. tetraphylla, also known as the M. ternifolia is similar in appearance M. jansenii is smaller than other rough-shelled nut, has a similar height to M. integrifolia and M. tetraphylla Macadamia species, reaching a and distribution to M. integrifolia. It can however it is a smaller tree, growing to height of 6–9m. First discovered in be distinguished by pink-purple flowers around 10m, and produces small nuts 1982, it is only known from an area and having leaves with spiked margins (around 2cm including outer green west of Miriam Vale in Queensland. that are arranged in groups of four on shell) that are bitter and slightly toxic. The inedible nuts are quite small at branchlets. New leaves of M. tetraphylla The leaves are sharp-tipped with some around 1.5cm. are bright red in colour, whereas M. spikes along the margin, arranged in Photos: CSIRO Plant Industry integrifolia are light green. Nut-shells groups of three on the branchlets. are roughened the raw nut kernels New growth is pink-red and flowers have a slightly grey tint and sweeter are pinkish. flavour than M. integrifolia nuts. Macadamia species in north Queensland Macadamia claudiensis Macadamia grandis Macadamia whelanii Photo: B. Gray © Centre for Plant Photo: CSIRO Plant Industry Photo: J. Connors © Centre for Plant Biodiversity Research Biodiversity Research M. grandis is from the Cairns region and M. claudiensis is located in rainforests reaches 10–40m in height. The leaves are M. whelanii can be found in lowland of the Cape York Peninsula region. in groups of four, with slightly wavy and coastal rainforest between Mount Leaves have smooth edges without margins without spikes. Flowers are Bellenden Ker to Mossman in Far North spikes and are in groups of five or six. yellow-cream, and nuts are up to 7cm Queensland. Leaves are mainly in It grows to 25–30m in height and has wide including the outer shell. It is groups of five on the branchlets, and white flowers. The nuts including the unknown whether the nuts are toxic. are without spikes. Unlike M. tetraphylla outer shell are very large, up to 8cm and M. integrifolia, the yellow flowers wide, and do not have a bitter flavour grow upwards from the branch. The large like many other Macadamia species so nuts are around 5cm in diameter including may not be toxic. the outer shell and are slightly toxic. Queensland nut tree Macadamia integrifolia Cultural heritage Macadamia, Grevillea and Banksia belong to the same family. Macadamia nuts are of material and cultural importance to Aboriginal people. They are eaten whole or pressed to produce oil that is used as a liniment base or as a binder for ochres and clays used for face and body decoration and artwork. To crack the hard macadamia nut-shell, Aboriginal people used a base rock containing a groove to stop movement of the nut, placed a flat rock on top of the nut and used another “hammer” rock to hit the flat rock. This method causes less damage to the kernel than directly hitting the shell with a hammer or other implement. The first recorded cultivation of aMacadamia species was a M. integrifolia nut kernel planted in the Brisbane Botanical Gardens in 1858 by the superintendent, Walter Hill. This tree continues to produce nuts and has a girth of around 2.5m at its base. Conservation status M. integrifolia is listed as vulnerable under the Queensland Nature Conservation Act 1992 and the Commonwealth Environment Protection and Biodiversity Conservation Act 1999. Table 1 outlines the conservation status of the regional ecosystems (REs) with which M. integrifolia is associated. Table 1. Regional ecosystems with which Macadamia integrifolia is associated and their status. RE Queensland Vegetation RE description *** Biodiversity Management Status * Status ** 12.3.1 Endangered Endangered Gallery rainforest/notophyll vine forest on alluvial plains 12.8.3 No concern at Not of concern Complex notophyll vine forest on present Cainozoic igneous rocks, altitude <600m 12.11.10 No concern at Not of concern Notophyll vine forest ± Araucaria present cunninghamii on metamorphics ± interbedded volcanics 12.12.16 No concern at Not of concern Notophyll vine forest on Mesozoic present to Proterozoic igneous rocks * Biodiversity Status as listed by the Environmental Protection Agency. ** Queensland Vegetation Management Act 1999 status as of December 2005. *** Refer to the Regional Ecosystem Description Database (REDD) at www.epa.qld.gov. au/nature_conservation/biodiversity/regional_ecosystems/ for full RE descriptions. Threats to M. integrifolia Land clearing for agricultural and urban development is the greatest threat to M. integrifolia. South-east Queensland, particularly in coastal areas, has experienced the highest rate of population growth and associated development in Queensland.